How to transfer your number from O2 to Three Mobile?

1) Check you’re eligible to switch from O2

If you’re out of contract, you can switch whenever you like for no charge. To check if you’re out of contract, you can:

Open your O2 app on your phone. Once it’s open, head to ‘Allowances’ and then select ‘Tariff’ to see your end date.

Or visit the O2 account webpage. Then click ‘See if you can upgrade today’ and log in to see your contract end date.

Prefer to call? You can get in touch with O2's customer support team by calling 202 on your O2 phone. Or on 034 4809 0202 from any other phone (standard network charges apply).

Opening hours are 8am-8pm Monday-Friday. 8am-6pm on Sundays.

In the event that you’re keeping your existing phone and signing up for a new SIM only deal, you may need to unlock your O2 phone. Only when it’s unlocked will it accept the new SIM card.

To unlock it, though, you’ll need what’s called a personal unlocking key (PUK). The good news is that you can obtain easily by logging in to your O2 account. Once you’ve got the PUK, which you’ll receive as a text message, you can use it to unlock your phone.

And if you’re interested in switching but want a bit more information first, text INFO to 85075.

2) Contact O2 to get your PAC code

Once you’ve signed up for the deal you’ve chosen, just text PAC to 65075 to get your PAC code. It’s this short, alphanumeric code that will enable you to transfer your existing phone number to the network you want to join.

If you'd prefer to speak to somebody, just ring O2 on one of the numbers in step 1 and tell them you want to leave. They’ll give you a contract end date that you should make a note of.

While you’re on the phone to them, you also need to ask for your PAC Code.

O2 is bound by law to provide a PAC Code within two hours of you asking for it.

3) Find and buy a new phone or SIM deal from Three

Out of contract and ready to switch? Good news. Your next task is to sign up for a new phone contract or SIM only deal from Three. Once you’ve passed Three’s credit checks, you’ll receive your phone in the post.

4) Contact Three to give them your PAC code

We’re almost there now. Next you’ll just to ring Three to give them your PAC. You can reach their customer support team on 0333 338 1001 from a landline (standard network rates apply).

5) Insert your new Three SIM card

If you got a new phone as part of your contract, take the pin-key included in the box and unlock the handset's SIM tray. Then insert your Three SIM card.

If you went for a SIM-only deal instead, you can just put the Three SIM in your existing phone.

While the number transfer is taking place, you’ll be given a temporary phone number that you can use and on which people can contact you.

6) Wait for your number to be transferred

The transfer should be complete the next working day. However, this can vary from network to network and sometimes depends on whether the day after you make your call is a working day or a weekend.